Single parents are being denied billions of pounds in unpaid child maintenance payments, which may never be collected.

The Department for Work and Pensions (DWP) has been accused of ‘writing off’ a staggering £2.9bn of the £3.9bn in missed child maintenance payments.

The Child Support Agency (CSA) was set up 21 years ago and tasked with chasing down absent parents, who snub their parental duty to contribute to the cost of raising their children.

However, the CSA was proven to be inefficient in getting absent payments to pay up, frequently dogged by computer software problems and was replaced by The Child Maintenance Service (CMS) in 2012.

The new system does not prioritise old debts on CSA records, despite around 1.3 million single parents being owed money from ex-partners.

Turning to the CSA after being made redundant from her job as a publicist in 2008, Marianne Miles from London is still owed a total of £12,000 in child maintenance payments.

Marianne’s ex-partner was ordered by the CSA to contribute in the cost of raising his teenage son – who is now 20 and at university – but no payments were ever collected.

Janet Allbeson, from the charity Gingerbread, said the Government should seek to recover historic unpaid child maintenance.

Speaking to BBC News, Jane Allbeson said: “If they do manage to get the money, even if it is years late, it can really make a difference to a child’s life.

“It allows, for instance, to help with the cost of going to college, perhaps paying off a student loan, or helping a child learn to drive.

“Children in some ways get more expensive as they get older and that money can make a real difference to a child’s future.”

Marianne says that even though her son is now grown up and at university, it “doesn’t mean he doesn’t need it now”, but she fears her son will never see the money.

“He’s a student so it could go towards his books and his food, that I have to support, and he’s learning how to drive. I’m the only person around to help him.”

“If he owed the government council tax money, or for a parking ticket, they would pursue it and make sure it was paid. But when it’s paying maintenance towards your own child, it is not deemed as important”, she said.

The Government has denied claims that old child maintenance debts have been ‘written-off’.

Pensions Minister Steve Webb said: “We are quite clear that just because money has been owed for a long time it does not mean it should be forgotten about. It should be paid.

“Of course everything cannot be a priority. We have been quite transparent… and we have made it clear that where there is a child still at school or being brought up – that is the first priority.

“But we are not writing off or ignoring old debt.”

The DWP said only £244 million is permanently “uncollectable”. The department uses the term to list cases where no payments have been made in the last six months, or where no plan to collect arrears is in place.

Helen Goodman MP, Labour’s Shadow Minister for Welfare Reform, said:

“Under the Government’s new scheme half of parents are getting less than they are entitled to or even nothing at all.

“This is money children are entitled to and a key plank in the fight against poverty.

“Arrears are at an all-time high of nearly £4 billion, of which the government has classed £2.9 billion as ‘uncollectible’.

“David Cameron’s government said they would tackle this. They haven’t and they’ve failed. It’s another example of Tory Welfare Waste.”